1. Serum aminotransferases Alanine aminotransferase and aspartate aminotransferase are mainly found in liver cells, and their concentrations in liver cells are 1,000 to 5,000 times higher than those in the blood. If damage occurs to liver cells due to inflammation, these enzymes within the cells are released into the blood, causing an increase in serum aminotransferases. Therefore, serum aminotransferases are the most sensitive indicator of liver cell damage. However, when there is extensive necrosis of liver cells (e.g. fulminant hepatitis) and the intrahepatic aminotransferases have been depleted, the elevation of serum aminotransferases can be insignificant. 2. Bilirubin Under normal circumstances, bilirubin needs to be processed by the liver and then discharged from the body through the bile duct. The bilirubin processed by the liver is called direct bilirubin, and the unprocessed bilirubin is called indirect bilirubin. The sum of direct bilirubin and indirect bilirubin is total bilirubin. Total bilirubin can be elevated in hepatocellular lesions, and indirect bilirubin is predominantly elevated, indicating a decrease in detoxification capacity. However, the liver has a strong ability to compensate for the metabolism of bilirubin, so total bilirubin and indirect bilirubin may not be elevated in the early stage of the disease. 3. Albumin and globulin Albumin is synthesized by the liver, and its concentration decreases may indicate impaired synthesis function of hepatocytes. However, the half-life of albumin is long, about 15-20 days, so the concentration of albumin can be normal in patients in the acute stage. Decreased albumin levels and increased globulin levels are common in patients with cirrhosis. The normal ratio of albumin to globulin is 1.5~2.5. If the ratio of albumin to globulin is <1, the medical term is "inversion of albumin/globulin ratio", which is one of the clinical features of cirrhosis. 4.Total cholesterol and cholinesterase Hepatocytes are involved in the synthesis and metabolism of cholesterol and cholinesterase, and these two indicators reflect the reserve function of the liver and the ability to recover from the disease. 5.Alkaline phosphatase and glutamyl transpeptidase Serum alkaline phosphatase and glutamyl transpeptidase are important indicators of biliary stasis. In cases of intra- and extrahepatic biliary obstruction (e.g., tumors, stones), they are significantly elevated simultaneously due to poor bile excretion and are often accompanied by a rise in direct bilirubin. Children and adolescents may have elevated single alkaline phosphatase due to bone development, which is a normal physiological phenomenon and should not be mistaken for abnormal liver function. 6.Fetoprotein Strictly speaking, fetoprotein is not a liver function test item, but sometimes doctors will ask for it, and it has a double meaning. Firstly, mild elevation indicates hepatitis activity and active hepatocyte regeneration, which is especially meaningful for heavy hepatitis, indicating that the patient is expected to recover; secondly, long-term significant elevation often indicates liver cancer, and it is generally believed that when AFP exceeds 500 ng/L for more than 4 weeks, or 200~500ng/L for more than 5 weeks, you should be highly alert to the possibility of liver cancer. It should be noted that elevated fetoprotein can also occur in pregnant women, but this is due to embryonic development and should not be confused with liver disease.